Desiccation apparatus and method

ABSTRACT

A desiccating device and method providing variable drying conditions allowing the desiccated material to substantially maintain its natural characteristics upon rehydration as well as have a low microbial content. The method provides a process of subjecting the material to ultrasound and flowing hot air or gas for a defined period of time. The ultrasonic frequency, temperature, air flow and time of exposure can be varied to produce the most efficient drying conditions depending on the material to be dried. The apparatus has plurality of drying chambers with forced heated air or gas input and output ducts and ultrasonic emitter. The material passes through each chamber at a pre-determined rate on a perforated conveyor belt in one embodiment of the invention. Optionally, the material may be placed on a drying bed or substrate comprising a number of spheres.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from U.S. provisionalapplication serial No. 60/235,066 filed on Sep. 25, 2000.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not Applicable

REFERENCE TO A COMPUTER PROGRAM APPENDIX

[0003] Not Applicable

BACKGROUND OF THE INVENTION

[0004] 1. Field of the Invention

[0005] This invention pertains generally to dehydration devices andmethods, and more particularly to a desiccation method and apparatuswith multiple dehydration zones utilizing ultrasound, heated circulatingair and a substrate matrix.

[0006] 2. Description of the Background Art

[0007] The preservation of food and other organic and inorganic materialby the evaporation of water from the material is well known in the art.Dehydration allows food to be kept for longer periods of time withoutrefrigeration. The size and weight of the food is reduced by dehydrationand the cost of transportation and storage of the food is thereforeminimized.

[0008] Early methods of dehydration consisted of placing whole or dicedfood articles on trays and setting the trays in the sun for several daysto allow the food to dry. This method proved to be undesirable on acommercial level because of the accumulation of dust, molds and otherair-borne particles on the food as well as the discoloration of the foodthat often occurs upon exposure of food to ultra-violet light.Furthermore, microbial levels in sun-dehydrated foods were oftenunpredictable and unacceptable with these early methods.

[0009] Mechanical kiln type dehydrating devices that isolated the foodfrom sunlight and outside air were then developed. These devices passedheated air through perforated trays until the water content of the foodparticles was reduced to a desired level. However, these methods did notappreciably change the presence of microbiological contaminants in manydehydrated foods, particularly those that were dried at relatively lowtemperatures for comparatively long periods of time. Although animprovement over sun dehydration, the kiln type dehydration devicesstill produce discolored foods in many instances due in part to thelength of time required to dry the foods.

[0010] In order to preserve the natural color and texture, manydehydrated fruits were treated with sulfur dioxide, sulfites or otherchemical preservatives. For many people, the taste of the preservativesmade the treated foods undesirable. For others, the preservatives poseda health risk leading to legislation limiting the amount and types ofpreservatives that could be present in various dehydrated foods.

[0011] Later methods sought to eliminate enzyme activity and reduce thelevels of bacteria and the like by blanching the food with steam or hotwater and then drying the food at high temperature. Unfortunately,blanching may alter the flavor and texture of some foods and may makeother foods difficult to dehydrate because the food absorbs water duringthe blanching process. Likewise, some foods are sensitive to exposure toheat. High drying temperatures may also adversely affect the color andflavor of dehydrated foods. Furthermore, blanching methods are notalways effective in consistently reducing the microbial levels toacceptable levels.

[0012] Recently developed methods of dehydration include treating thefood with an osmotic agent and then dehydrating the food with heatedair. Still other methods use heated vegetable oil and treatment inreduced pressure environments. These methods are unsatisfactory due tothe residues left by the treating agents as well as the expense ofproduction.

[0013] Substantially microbe free dehydrated foods have been produced by“freeze-drying” methods known in the art. Fruit and vegetable productsare typically frozen and the water removed by sublimation in alow-pressure environment with these methods. The cost of high capacityrefrigeration systems and low-pressure systems, as well as the cost ofenergy and maintenance, makes the resulting food product expensive tomanufacture using these methods.

[0014] Some seasonal vegetables, such as onions and bell peppers have alimited market life. For example, onions that are beyond certain sizelimits are often tilled under in the field or composted because theonions cannot be brought to market during the season. As much astwenty-five percent of the yearly onion crop may be wasted in thismanner.

[0015] Only a small percentage of onions are currently dehydratedbecause of the difficulty experienced dehydrating onions using currentmethods. Presently, yellow onions may be frozen to preserve the onionuntil the onions can be processed. In addition, diced pieces of onion donot dry well because the pieces tend to stick together due to the sugarcontent of the onion thereby creating pockets of moisture. Bacteria arefound in such moisture pockets requiring the destruction of the onionpieces resulting in additional waste and expense.

[0016] Materials other than food, such as medicinal herbs, may beprepared using dehydration to provide material for encapsulation or thelike. Dehydration may also be used in the processing of sludge or otherorganic matter as well as inorganic matter.

[0017] Accordingly, the principal challenge to current desiccationmethods is to generate a dehydrated product with natural colors,textures and flavors that is free from microbiological contamination andnoxious residues. Thus, there is a need for an effective and costefficient desiccating apparatus and method that can maintain the naturalcolor, flavor and texture of the food while keeping the microbial levelwithin acceptable limits without using additives or preservatives orcostly desiccation machinery and methods. The present inventionsatisfies these needs, as well as others, and generally overcomes thedeficiencies found in existing equipment and methods.

BRIEF SUMMARY OF THE INVENTION

[0018] The present invention is a material desiccation apparatus andassociated method for producing dehydrated vegetables and the like, thatare substantially free of microbiological contaminants and retain thenatural color, flavor and texture of the vegetable upon rehydration. Theapparatus and method are particularly suited for dehydrating vegetablessuch as onions that discolor using current methods known in the art.However, the apparatus and method may also be used to dehydrate non-foodmaterials such as sludge as well as inorganic materials.

[0019] By way of example, and not of limitation, the inventive methodcomprises circulating a heated gas, such as air, over prepared and sizedfood material, and optionally subjecting the material to ultrasonicsound waves, until the moisture content of the material is preferablyreduced to approximately 5% to 10% of its original content. The time ofexposure, the ultrasonic wavelength, the volume of gas, rate of gasflow, and the temperature of the circulating gas can be varied in singleor multiple stages to control the overall rate of desiccation of thematerial. In this way, the conditions and rate of desiccation and can betailored to the characteristics and type of food or other material to bedehydrated. The exposure of the material to ultrasound and the exposureto circulating gas are preferably done simultaneously. However, theexposures may also be done in close succession.

[0020] The preferred method of using the apparatus of the presentinvention, applied to onions for example, will have at least one stageand preferably three dehydration stages. While the preferred method hasthree stages, it will be seen that any number of stages can be utilized.

[0021] In the preferred first stage, the prepared and sized onions aresimultaneously subjected to ultrasound, preferably at frequencies withinthe range of approximately 20 KHz to approximately 100 KHz, andcirculating heated air at a temperature within the range ofapproximately 190° F. to approximately 200° F. for a period ofapproximately 13 to approximately 15 minutes. The flow of air ispreferably approximately 240 cubic feet per minute per square foot ofdrying bed in the first stage. The ultrasonic emissions may becontinuous or pulsed.

[0022] During the second stage, the onions are exposed to ultrasound atfrequencies within the range of approximately 20 KHz to approximately100 KHz and circulating heated air at a temperature within the range ofapproximately 170° F. to approximately 180° F. for a period ofapproximately 13 to approximately 15 minutes. The flow of air ispreferably approximately 180 cubic feet per minute per square foot ofdrying bed in the second stage.

[0023] In the third and final stage, the onions are subjected toultrasound at frequencies within the range of approximately 20 KHz andapproximately 100 KHz and circulating heated air at a temperature withinthe range of approximately 150° F. to approximately 160° F. for a periodof about 60 minutes or as needed to bring the water content of the onionpieces to approximately 5% by weight. The preferred airflow is around150 cubic feet per minute per square foot of drying bed in this example.

[0024] While the method is tailored for onions as an example, it will beunderstood that the temperature, ultrasonic frequencies, number ofstages, volume of circulating gas and time of exposure may be varied ineach stage depending on the type of material to be dehydrated.Additionally, the use of ultrasound is optional and its use, as well asthe stages in connection with which ultrasound is used, can varydepending on the particular product being dried.

[0025] According, the apparatus of the present invention generallycomprises a drying chamber having an optional ultrasound generator alongwith intake and output ducts to allow heated air to circulate in andthrough the chamber and out of the chamber. The food material ispreferably placed on a substrate comprising a plurality of spheres.Although the spherical shape is preferred, it will be understood thatany shape substrate may be used.

[0026] The preferred embodiment has an elongate enclosure with a numberof vertical partitions defining three drying chambers. Each dryingchamber has an ultrasound emitter and air intake and output ductwork. Ahorizontal, perforated conveyor belt, preferably with a number ofvertical vanes, runs longitudinally through the enclosure andpartitions. The endless conveyor belt is preferably motorized.

[0027] The spheres and food material are placed between the verticalvanes of the conveyor belt to a depth of about 24 inches or less.Alternatively, the spheres and food material may be placed in aperforated container. The ultrasound emitter and intake duct in eachdrying chamber are preferably positioned below the perforated conveyorbelt and the output duct above the conveyor.

[0028] In use, the spheres with the food material advance along theperforated conveyor to the enclosure and the first drying chamber.Heated air is brought through the intake duct and forced through theperforated belt, around the spheres and the food particles to the uppersection of the chamber and out through the output duct. After a definedperiod of time, the belt advances through a partition into the seconddrying chamber. The second and third drying chambers are preferablyconfigured in the same manner as the first drying chamber. However, thetemperature of the input air and the frequency of the ultrasound and thetime of exposure may be different from chamber to chamber. Optionally,the air intake of the second drying chamber may be joined to the intakeduct of the third drying chamber, and so on, to conserve the heat.

[0029] After exiting the enclosure, the spheres are removed from theconveyor belt and the desiccated food material is separated from thespheres and thereafter prepared for packaging. In one embodiment, thespheres and dried food particles are placed on a vibrating perforatedtable to separate the spheres from the dehydrated material.

[0030] An object of the invention is to provide an apparatus and methodto efficiently dehydrate material without being required to blanch,freeze or treat the material with preservatives.

[0031] Another object of the invention is to provide a modular,multi-stage desiccating apparatus that can efficiently and economicallydehydrate material by subjecting the material to ultrasound and acirculating heated gas in each stage.

[0032] A further object of the present invention is to provide adesiccating apparatus and method that will greatly reduce bacteria andother microbial levels without significantly affecting the flavor,texture and other characteristics of the dehydrated materials uponrehydration.

[0033] Another object of the invention is to provide a device that hasvariable desiccating conditions that can be adapted to provide a rangeof dehydration rates allowing the efficient dehydration of a variety offoods and other materials.

[0034] Yet another object of the invention is to provide a supportsubstrate that supports the material to be dehydrated to allow fasterand more efficient dehydration than found in conventional dehydrationdevices.

[0035] Further objects and advantages of the invention will be broughtout in the following portions of the specification, wherein the detaileddescription is for the purpose of fully disclosing preferred embodimentsof the invention without placing limitations thereon.

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The invention will be more fully understood by reference to thefollowing drawings, which are for illustrative purposes only:

[0037]FIG. 1 is a perspective view of an embodiment of a desiccatingapparatus according to the present invention having three stages.

[0038]FIG. 2 is a side view of the desiccating apparatus of FIG. 1showing the vaned conveyor belt configuration.

[0039]FIG. 3 is a side view of the desiccating apparatus of FIG. 1 withintake ducts, ultrasound emitters and belt portions depicted in dashedlines.

[0040]FIG. 4 is a detailed partial interior side view of the first stageof the desiccation apparatus of FIG. 1 shown with the support substratein one section of the drying bed.

[0041]FIG. 5 is a detailed side view of one section of the drying bedshown in FIG. 4.

[0042]FIG. 6 is a side view of the separator portion of the apparatusshown in FIG. 1 showing the separation of the dehydrated material fromthe support substrate.

[0043]FIG. 7 is a side view of an alternative embodiment of the presentinvention showing the ductwork connecting the output duct of one dryingchamber with the input duct of the subsequent chamber allowing heat tobe conserved.

DETAILED DESCRIPTION OF THE INVENTION

[0044] Referring more specifically to the drawings, for illustrativepurposes the present invention is embodied in the apparatus generallyshown in FIG. 1 through FIG. 7, where like reference numbers denote likeparts. It will be appreciated that the apparatus may vary as toconfiguration and as to details of the parts, and that the method mayvary as to the specific steps and sequence, without departing from thebasic inventive concepts disclosed herein.

[0045] Referring first to FIG. 1, the desiccation apparatus 10 accordingto the present invention preferably comprises multiple linearly arrangeddrying chambers through which an endless horizontal conveyor belt 12generally moves in one direction. These drying chambers are essentiallystages or zones in an enclosure 14 through which the material to bedried can pass. Three stages are provided in the embodiment shown inFIG. 1.

[0046] Conveyor belt 12 may optionally have vertical vanes 16 that aregenerally perpendicular to the horizontal plane of the belt 12. A motor18 is mounted to enclosure 14 and provides motion to the conveyor belt12 at variable speeds as needed. Motor 18 may have step down gearingwith a first sprocket 20 and a second sprocket 22 to regulate the rateof advancement of conveyor belt 12 through the enclosure 14. Theconveyor belt 12 may quickly advance through each stage at designatedtime points or may alternatively move very slowly through the stageswhen the desired time of exposure of the material in each stage isessentially the same.

[0047] Enclosure 14 has a front entry panel 24 and a rear exit panel 26.The front and rear panels 24, 26 extend vertically from the top of theenclosure to just above the tip of the vanes 16 of the conveyor belt 12so as not to interfere with the passage of the belt 12 through theinterior of enclosure 14. The front and rear panels 24, 26 may be madeof rigid steel or, alternatively, flexible plastic and are configured toreduce the flow of air into or out of the enclosure 14 through the placeof entry or exit of conveyor belt 12 from the enclosure 14.

[0048] Referring also to FIG. 2 and FIG. 3, it can be seen thatenclosure 14 has a top wall 28, and a bottom or floor 30 that issupported by a left sidewall 32, and a right side wall 34. The enclosure14 and conveyor belt 12 are preferably supported by a plurality ofsupport legs 36 to position belt 12 at a level that will allow a workerto place materials on conveyor belt 12 without bending over.

[0049] Referring particularly to FIG. 2, in the embodiment shown theinterior of enclosure 14 is divided by inner vertical partitions 38 and40 to define discrete drying chambers. Partition 38 forms a first dryingchamber 42. Partition 40 forms a second drying chamber 44 and a thirddrying chamber 46 within enclosure 14. Both partitions 38 and 40 have anopening to allow conveyor belt 12 and vanes 16 to move freely throughdrying chambers 42, 44 and 46. Conveyor belt 12 advances horizontallythrough enclosure 14, around a powered roller 48, below floor 30 andbetween the support legs 36 to trailing roller 50. Alternatively, aperforated container or platform (not shown) may be used instead of thevanes 16 of perforated conveyor 12 to hold the material to bedehydrated.

[0050] Drying chamber 42 has an ultrasound emitter 52 preferablypositioned below conveyor belt 12 at or near bottom wall 30 of enclosure14. Likewise, the second and third drying chambers 44, 46 haveultrasound emitters 54 and 56 respectively positioned below belt 12within enclosure 14.

[0051] Each drying chamber preferably has discreet intake and outputducts that allow heated air or gas to be directed through each dryingchamber. The volume and rate of flow of gas through each of the inputducts for each chamber can be varied.

[0052] Intake duct 58 is positioned below conveyor belt 12 in the firstdrying chamber 42. Conveyor belt 12 is preferably perforated to allowair to flow through the belt. Output duct 60 is preferably positioned atthe top of wall 28 of the enclosure and first drying chamber 42.Likewise, the second drying chamber 44 has input duct 62 and output duct64 and the third drying chamber 46 has input duct 66 and output duct 68in similar configuration to the ducts of the first drying chamber 42.While the input ducts and ultrasound emitters are preferably placedbelow the perforated conveyor belt 12, it will be understood that theultrasound emitters 52, 54, and 56 can be placed above the conveyor belt12 and the air flow can come from either above, below or to the side ofbelt 12 depending on the placement of input ducts 58, 60 and 62.

[0053] It can be seen that enclosure 14 is modular. One or more dryingchambers can be sequentially added as needed to the first dryingchamber, each chamber having input and output ducts and, optionally, anultrasound emitter. The chambers may be contiguous as in the embodimentshown or independent of the other chambers.

[0054] The temperature of the air or gas that enters each drying chamber42, 44, 46 can be raised by heating the intake air or gas using afurnace or other methods known in the art and commercially available.The gas or air is forced through the furnace elements and heated in thisembodiment. The air then proceeds into the first drying chamber 42 andis then preferably drawn out of the chamber by a number of fans known inthe art. The fans should be capable of moving volumes of air fromapproximately 150 to approximately 450 cubic feet per minute per squarefoot through the drying chambers 42, 44 and 46. The volume of airdirected through each drying chamber can be increased or decreased toinfluence the overall rate of dehydration by the apparatus.

[0055] For drying certain materials, it may be desirable to use a heatedinert gas such as Nitrogen as a medium rather than heated air to reducethe amount of oxidization of the material. Accordingly, the system couldbe closed and the inert gas recycled without departing from the scope ofthe invention.

[0056] To conserve heat, a heat exchanger known in the art (not shown)may be associated with output duct 60, as well as associated air ducts,to transfer heat from the air exiting the first drying chamber 42 to theincoming air of the second drying chamber 44 through intake duct 62.Heat exchangers may also be associated with each output duct from eachdrying chamber to heat the air or gas entering the input ductwork ofeach drying chamber.

[0057] Referring also to FIG. 4 and FIG. 5, the invention preferablyincludes a drying bed that utilizes a support substrate. The supportsubstrate preferably comprises a plurality of spheres 70 held withinvertical vanes 16 of conveyor belt 12 to form the drying bed. Each areabetween each of the vanes 16 is filled with spheres 70 and foodparticles 72. For clarity, FIG. 4 and FIG. 5 show only a single spacefilled between vanes 16. Alternatively, the spheres 70 and foodparticles 72 may be placed in an open container with perforated wallsand bottom to support the drying bed that is placed on a perforatedconveyor or other support structure.

[0058] Spheres 70 are preferably approximately ¾ of an inch in diameterand are made of heat resistant plastic or similar material. The size ofthe spheres may be increased or decreased depending on the type ofmaterial that is to be desiccated and the size of the particles that areintroduced into the apparatus. Food particles, or other material 72 andspheres 70 can form a drying bed of varying depths, but the bedpreferably has a depth of approximately twenty-four inches or less inthe embodiment shown. A drying bed of this type facilitates fasterdrying because the spheres separate the product and increase the exposedsurface area of the product. While the drying bed is preferably composedof spheres, it will be understood that the drying bed could be composedof solids of virtually any shape. The use of spheres or balls inconnection with drying materials is described in more detail in my priorpatent, U.S. Pat. No. 5,522,156 issued on Jun. 4, 1996, incorporatedherein by reference.

[0059] In use, food particles 72 or other items to be desiccated aremixed with spheres 70 and placed on a loading section of perforatedconveyor belt 12 within sectioned areas formed by vertical vanes 16 andleft and right loading area sidewalls 74, 76. In the embodiment shown,belt 12 and the material to be dehydrated advance through the frontentry panel 24 and into the first drying chamber 42. Heated air isbrought into chamber 42 through intake duct 58 and forced through theperforations of conveyor belt 12. The air then circulates through thespaces between spheres 70 and food particles 72 and is drawn out of thechamber through output duct 60. At the same time the food particles 72are preferably subject to pulsed or constant ultrasonic emissions fromultrasound emitter 52.

[0060] At the appropriate time, the food or other matter is conveyedfrom the first drying chamber 42 to the second drying chamber 44 throughan access way through partition 38. Air or other heated gas enterschamber 44 through intake duct 62 and is forced through the perforatedconveyor belt 12 and around spheres 70 and food particles 72 and out ofthe chamber through output duct 64. At the same time, the food particles72 are exposed to ultrasonic emissions from ultrasound emitter 54.Emitter 54 may be set to emit ultrasonic waves at a different frequencyfrom emitter 52 in the first drying chamber or may be set at the samefrequency depending on the type of food material 72 to be dehydrated.The temperature and volume of the heated air or gas entering chamber 44may also be variable.

[0061] The material then enters the third drying chamber 46 through anaccess way through partition 40. Heated air or gas enters the thirddrying chamber 46 though intake duct 66 and is forced through belt 12around spheres 70 and food particles 72 and out through output duct 68.Emitter 56 provides pulsed or constant ultrasonic emissions to the thirddrying chamber 46 at desired frequencies.

[0062] Finally, the materials exit the third drying chamber 46 andenclosure 14 through rear exit panel 26. Referring to FIG. 6, thedehydrated food particles 72 are separated from spheres 70 using avibrating table 78 or other commercial separator. Spheres 70 arereturned to a staging area for cleaning and mixing with new foodmaterial in the embodiment shown. The separated dehydrated foodparticles 72 are taken by conveyor 80 to be inspected and packaged.

[0063] Turning now to FIG. 7, a heat conserving alternative embodimentof the present invention is shown. In this configuration, the air fromthe output duct of the previous drying chamber is attached to the inputduct of the subsequent chamber to conserve heat. For example, outputduct 64 of the second drying chamber 44 may be connected to input duct66 of the third drying chamber 46 by a connecting pipe 82 with anoptional fan. The heated air from the second drying chamber 44 isrecycled through the third 15 drying chamber 46 thereby conserving heat.However, the water content of the air exiting the first drying chambermay often be too high to effectively recycle the air from the firstdrying chamber 42. If this is the case, the heat must be transferredthrough the use of a heat exchanger.

[0064] It will be understood by one skilled in the art that the dryingchambers could be separate rather than contiguous as shown in FIG.1through FIG. 7. For example, the time of exposure of the food particlesmay need to be different for each drying chamber requiring differentrates of advancement for the conveyor belt. Therefore, separate beltsand separate drying chambers would be used without departing from thescope of the invention.

[0065] In practicing the methods of the invention, the matter to bedesiccated is initially prepared. The methods of the present inventionare particularly suited for desiccation of fruits and vegetables andother plants as well as shrimp and certain cut meats. Accordingly,preparation may include washing, peeling, cutting, dicing, andprecooking and the like depending on the material to be dehydrated.

[0066] The prepared particulate food matter is then loaded into anapparatus that is capable of providing variable temperature, gas orairflow and pulsed or constant ultrasonic emissions over time. Thetemperature, rate of airflow and the frequency of ultrasonic emissionand the sequence of exposures may vary depending on the type of materialthat is to be dehydrated. The inventive methods also contemplate thatthe ultrasonic frequency could be zero when the spherical supportsubstrate 72 is utilized in appropriate circumstances. It will be seenthat the variation of temperature, airflow, time of exposure as well asthe frequency of the ultrasonic emissions may regulate the overall rateof desiccation.

[0067] In order to further illustrate the inventive methods of thepresent invention, the following non-limiting example is provided. Inthis example, onions are washed, peeled and diced. The prepared dicedonions are preferably mixed with spheres 70 and loaded onto a perforatedconveyor 12. In phase one (drying chamber 42), the onions are exposed tocontinuous ultrasound at a frequency of approximately 20 KHz, and tocirculating heated air at a temperature between approximately 190° F.and approximately 210° F., preferably approximately 200° F. at a rate ofapproximately 240 cubic feet per minute per square foot of drying bedfor approximately fifteen minutes. As much as 70% of the water contentof the onion is removed in this phase as a result of the sphericalsupport substrate and the ultrasound exciting the water molecules andthe movement of water to the outer surface of the onion.

[0068] In phase two (drying chamber 44), the diced onion is subjected tocontinuous ultrasound at a frequency of approximately 20 KHz, and tocirculating heated air at a temperature between approximately 170° F.and approximately 190° F., preferably approximately 180° F. at a rate ofapproximately 180 cubic feet per minute per square foot forapproximately fifteen minutes.

[0069] Finally, In phase three (drying chamber 46), the diced onion isthen subjected to continuous ultrasound at a frequency of approximately20 KHz, and to circulating heated air at a temperature betweenapproximately 150° F. and approximately 170° F., preferably 160° F., ata rate of approximately 150 cubic feet per minute per square foot ofsurface area for approximately one hour until the moisture content ofthe onion is approximately 5%. This level of moisture content makes theproduct shelf stable; that is, it will have an indefinite shelf life.The onion is then inspected and packaged.

[0070] By staging the drying process as described, the expulsion ofmoisture is maximized without damaging the food. As the amount of solidsincreases due to a reduction in moisture, the sensitivity of the foodproduct to temperature increases. Accordingly, the drying temperaturemay be dropped in successive drying zones. Furthermore, by subjectingthe material to ultrasonic sound waves, the water molecules in thematerial are excited and move to the outer surface of the material, thusallowing for more efficient drying by the circulating heated gas.

[0071] Current permissible bacterial counts in onions dehydrated usingconventional means have a standard total plate count of approximately300,000. Plate counts of 10,000, which are well below permissiblelevels, have been observed in onions using the apparatus and methods ofthe present invention.

[0072] Accordingly, it will be seen that the methods and apparatus ofthis invention can efficiently and swiftly desiccate food particleswhich are substantially free of microbial content without the need forblanching, freezing, dehydrating at low pressures, chemical treatmentsor other activities that may affect the color, flavor and texture of thefood upon rehydration.

[0073] Although the description above contains many specificities, theseshould not be construed as limiting the scope of the invention but asmerely providing illustrations of some of the presently preferredembodiments of this invention. Therefore, it will be appreciated thatthe scope of the present invention fully encompasses other embodimentswhich may become obvious to those skilled in the art, and that the scopeof the present invention is accordingly to be limited by nothing otherthan the appended claims, in which reference to an element in thesingular is not intended to mean “one and only one” unless explicitly sostated, but rather “one or more.” All structural, chemical, andfunctional equivalents to the elements of the above-described preferredembodiment that are known to those of ordinary skill in the art areexpressly incorporated herein by reference and are intended to beencompassed by the present claims. Moreover, it is not necessary for adevice or method to address each and every problem sought to be solvedby the present invention, for it to be encompassed by the presentclaims. Furthermore, no element, component, or method step in thepresent disclosure is intended to be dedicated to the public regardlessof whether the element, component, or method step is explicitly recitedin the claims. No claim element herein is to be construed under theprovisions of 35 U.S.C. 112, sixth paragraph, unless the element isexpressly recited using the phrase “means for.”

What is claimed is:
 1. A method for producing dried foods, comprising:circulating a heated gas around said food product until said foodproduct has a moisture content within the range of approximately zero tofive percent.
 2. A method as recited in claim 1, further comprisingsimultaneously exposing said food product to ultrasonic waves andcirculating said heated gas around said food product.
 3. A method asrecited in claim 2, wherein said food product is exposed to ultrasonicwavelengths within the range of approximately 20 KHz to approximately100 KHz for approximately fifteen to ninety minutes.
 4. A method asrecited in claim 1, said method further comprising placing said foodproduct on a support substrate.
 5. A method as recited in claim 1,wherein said circulated heated gas comprises nitrogen.
 6. A method asrecited in claim 2, further comprising exposing said food product to asecond ultrasonic frequency and circulating heated gas at a secondtemperature for a second period of time.
 7. A method as recited in claim6, further comprising exposing said food product to a third ultrasonicfrequency and circulating heated gas at a third temperature for a thirdperiod of time.
 8. A method for producing dried foods, comprising:exposing a food product to ultrasonic waves; and circulating a heatedgas around said food product until said food product has a moisturecontent within the range of approximately zero to five percent.
 9. Amethod as recited in claim 8, wherein said steps of exposing said foodproduct to ultrasonic waves and circulating a heated gas around saidfood product are performed simultaneously.
 10. A method as recited inclaim 8, wherein said food product is exposed to ultrasonic wavelengthswithin the range of approximately 20 KHz to approximately 100 KHz forapproximately fifteen to ninety minutes.
 11. A method as recited inclaim 8, said method further comprising placing said food product on asupport substrate.
 12. A method as recited in claim 8, wherein saidcirculated heated gas is nitrogen.
 13. A method as recited in claim 8,further comprising exposing said food product to a second ultrasonicfrequency and circulating heated gas at a second temperature for asecond period of time.
 14. A method as recited in claim 13, furthercomprising exposing said food product to a third ultrasonic frequencyand circulating heated gas at a third temperature for a third period oftime.
 15. A process for desiccating a material containing moisture,comprising: placing said material onto a supporting substrate; exposingsaid object to sound waves having a first ultrasonic wavelength for afirst period of time; simultaneously circulating a heated gas at a firsttemperature around said material for said first period of time; exposingsaid prepared and sized material to sound waves having a secondultrasonic wavelength for a second period of time; simultaneouslycirculating a heated gas at a second temperature around said materialfor said second period of time; exposing said prepared and sizedmaterial to sound waves having a third ultrasonic wavelength for saidthird period of time; simultaneously circulating a heated gas at a thirdtemperature around said material for third period of time; andseparating said material from said substrate.
 16. A method ofdesiccating a material containing moisture according to claim 15,wherein said heated gas is circulated around said material and saidsupport substrate at a rate between approximately 150 cubic feet perminute per square foot and approximately 450 cubic feet per minute persquare foot.
 17. A method of desiccating vegetables, comprising:preparing and sizing the vegetables and placing the vegetables on asupport substrate; subjecting said vegetables to ultrasonic waves;circulating air heated to a temperature of approximately 190° F. toapproximately 210° F. around the vegetables for approximately fifteenminutes; circulating heated air at a temperature of approximately 170°F. to approximately 190° F. around the vegetables for approximately 15minutes; circulating heated air at a temperature of approximately 150°F. to approximately 170° F. around the vegetables for about one houruntil said vegetables have a moisture content of approximately 5%; andremoving the dehydrated vegetables from said support substrate.
 18. Amethod of desiccating vegetables according to claim 17, wherein saidheated air is circulated around said vegetables and said supportsubstrate at a rate between approximately 150 cubic feet per minute persquare foot and approximately 450 cubic feet per minute per square foot.19. An apparatus for producing dried foods, comprising: a housing havinga drying chamber; and means for circulating a heated gas around saidfood product until said food product has a moisture content within therange of approximately zero to five percent.
 20. An apparatus as recitedin claim 12, further comprising means for exposing said food product toultrasonic waves.
 21. An apparatus as recited in claim 20, wherein saidmeans for circulating a heated gas around said food product and saidmeans for exposing said food product to ultrasonic waves are configuredto simultaneously expose said food product to said ultrasonic waves andsaid heated gas.
 22. An apparatus as recited in claim 20, wherein saidmeans for exposing said food product to ultrasonic waves is configuredfor exposure at wavelengths within the range of approximately 20 KHz toapproximately 100 KHz for approximately fifteen to ninety minutes. 23.An apparatus as recited in claim 19, further comprising a supportsubstrate configured for carrying said food product.
 24. An apparatus asrecited in claim 19, wherein said circulated heated gas comprisesnitrogen.
 25. An apparatus for producing dried foods, comprising: ahousing having a drying chamber; means for exposing a food product toultrasonic waves; and means for circulating a heated gas around saidfood product until said food product has a moisture content within therange of approximately zero to five percent.
 26. An apparatus as recitedin claim 25, wherein said means for circulating a heated gas around saidfood product and said means for exposing said food product to ultrasonicwaves are configured to simultaneously expose said food product to saidultrasonic waves and said heated gas.
 27. An apparatus as recited inclaim 25, wherein said means for exposing said food product toultrasonic waves is configured for exposure at wavelengths within therange of approximately 20 KHz to approximately 100 KHz for approximatelyfifteen to ninety minutes.
 28. An apparatus as recited in claim 25,further comprising a support substrate configured for carrying said foodproduct.
 29. An apparatus as recited in claim 25, wherein saidcirculated heated gas comprises nitrogen.
 30. An apparatus for reducingthe moisture content in a food product, comprising: a housing; saidhousing having a first drying zone and a second drying zone; a conveyor;said conveyor configured to move said food product through said firstand second drying zones; a first heat source; said first heat sourceconfigured to circulate heated gas through said first drying zone at afirst temperature; and a second heat source; said second heat sourceconfigured to circulate heated gas through said second drying zone at asecond temperature.
 31. An apparatus as recited in claim 30, furthercomprising: an ultrasound source; said ultrasound source configured toexpose said food product in at least one of said drying zones toultrasonic waves.
 32. An apparatus as recited in claim 30: wherein saidfirst heat source is configured to circulate said gas through saidhousing at a rate of between approximately 150 cubic feet per minute persquare foot and approximately 450 cubic feet per minute per square foot;and wherein said second heat source are configured to circulate said gasthrough said housing at a rate of between approximately 150 cubic feetper minute per square foot and approximately 450 cubic feet per minuteper square foot.
 33. An apparatus as recited in claim 30: wherein saidfirst heat source is configured to circulate gas through said firstdrying zone at a rate of rate of between approximately 150 cubic feetper minute per square foot and approximately 450 cubic feet per minuteper square foot; and wherein said second heat source is configured tocirculate gas through said second drying zone at a rate of rate ofbetween approximately 150 cubic feet per minute per square foot andapproximately 450 cubic feet per minute per square foot.
 34. Anapparatus as recited in claim 30, further comprising: a supportsubstrate; said support substrate configured to carry said food product.35. An apparatus as recited in claim 34, wherein said support substratecomprises a plurality of spheres.
 36. An apparatus as recited in claim35, wherein said conveyor includes a plurality of vanes having anintermediate area containing said spheres.
 37. An apparatus as recitedin claim 35, wherein said spheres are held in a container placed on saidconveyor.
 38. An apparatus as recited in claim 31, wherein saidultrasonic source and at least one said heat source are configured tosimultaneously expose said food product to said ultrasonic waves andsaid heated gas.
 39. An apparatus as recited in claim 38, wherein saidultrasonic source is configured for exposure at wavelengths within therange of approximately 20 KHz to approximately 100 KHz for approximatelyfifteen to ninety minutes.
 40. An apparatus for reducing the moisturecontent in a food product, comprising: a housing; said housing having afirst drying zone and a second drying zone; a conveyor; said conveyorconfigured to move said food product through said first and seconddrying zones; a first heat source; said first heat source configured tocirculate heated gas through said first drying zone at a firsttemperature; a second heat source; said second heat source configured tocirculate heated gas through said second drying zone at a secondtemperature; and an ultrasound source; said ultrasound source configuredto expose said food product in at least one of said drying zones toultrasonic waves.
 41. An apparatus as recited in claim 40: wherein saidfirst heat source is configured to circulate said gas through saidhousing at a rate of between approximately 150 cubic feet per minute persquare foot and approximately 450 cubic feet per minute per square foot;and wherein said second heat source are configured to circulate said gasthrough said housing at a rate of between approximately 150 cubic feetper minute per square foot and approximately 450 cubic feet per minuteper square foot.
 42. An apparatus as recited in claim 40: wherein saidfirst heat source is configured to circulate gas through said firstdrying zone at a rate of rate of between approximately 150 cubic feetper minute per square foot and approximately 450 cubic feet per minuteper square foot; and wherein said second heat source circulates gasthrough said second drying zone at a rate of rate of betweenapproximately 150 cubic feet per minute per square foot andapproximately 450 cubic feet per minute per square foot.
 43. Anapparatus as recited in claim 40, further comprising: a supportsubstrate; said support substrate configured to carry said food product.44. An apparatus as recited in claim 43, wherein said support substratecomprises a plurality of spheres.
 45. An apparatus as recited in claim44, wherein said conveyor includes a plurality of vanes having anintermediate area containing said spheres.
 46. An apparatus as recitedin claim 44, wherein said spheres are held in a container placed on saidconveyor.
 47. An apparatus as recited in claim 40, wherein saidultrasonic source and at least one said heat source are configured tosimultaneously expose said food product to said ultrasonic waves andsaid heated gas.
 48. An apparatus as recited in claim 47, wherein saidultrasonic source is configured for exposure at wavelengths within therange of approximately 20 KHz to approximately 100 KHz for approximatelyfifteen to ninety minutes.
 49. An apparatus for reducing the moisturecontent in a food product, comprising: a housing; said housing havingfirst, second and third drying zones; a conveyor; said conveyorconfigured to move said food product through said drying zones; a firstheat source; said first heat source configured to circulate heated gasthrough said first drying zone at a first temperature; a second heatsource; said second heat source configured to circulate heated gasthrough said second drying zone at a second temperature; a third heatsource; said third heat source configured to circulate heated gasthrough said third drying zone at a third temperature; and an ultrasoundsource; said ultrasound source configured to expose said food product inat least one of said drying zones to ultrasonic waves.
 50. An apparatusas recited in claim 49: wherein said first, second and third heatsources are configured to circulate said gas through said housing at arate of between approximately 150 cubic feet per minute per square footand approximately 450 cubic feet per minute per square foot.
 51. Anapparatus as recited in claim 49: wherein said first heat source isconfigured to circulate gas through said first drying zone at a rate ofrate of between approximately 150 cubic feet per minute per square footand approximately 450 cubic feet per minute per square foot; whereinsaid second heat source is configured to circulate gas through saidsecond drying zone at a rate of rate of between approximately 150 cubicfeet per minute per square foot and approximately 450 cubic feet perminute square foot; and wherein said third heat source is configured tocirculate gas through said third drying zone at a rate of rate ofbetween approximately 150 cubic feet per minute per square foot andapproximately 450 cubic feet per minute per square foot.
 52. Anapparatus as recited in claim 49, further comprising: a supportsubstrate; said support substrate configured to carry said food product.53. An apparatus as recited in claim 52, wherein said support substratecomprises a plurality of spheres.
 54. An apparatus as recited in claim53, wherein said conveyor includes a plurality of vanes having anintermediate area containing said spheres.
 55. An apparatus as recitedin claim 53, wherein said spheres are held in a container placed on saidconveyor.
 56. An apparatus as recited in claim 49, wherein saidultrasonic source and at least one said heat source are configured tosimultaneously expose said food product to said ultrasonic waves andsaid heated gas.
 57. An apparatus as recited in claim 56, wherein saidultrasonic source is configured for exposure at wavelengths within therange of approximately 20 KHZ to approximately 100 KHz for approximatelyfifteen to ninety minutes.
 58. An apparatus for reducing the moisturecontent in food material, comprising: a housing; said housing having atleast one drying chamber; means for exposing said food material to soundwaves having a first ultrasonic wavelength for a first period of timeand simultaneously circulating a heated gas at a first temperaturearound said material for said first period of time; means for exposingsaid food material to sound waves having a second ultrasonic wavelengthfor a second period of time and simultaneously circulating a heated gasat a second temperature around said material for said second period oftime; means for exposing said food material to sound waves having athird ultrasonic wavelength for said third period of time andsimultaneously circulating a heated gas at a third temperature aroundsaid material for third period of time; and means for separating saidmaterial from said substrate.
 59. An apparatus for desiccating a foodproduct, comprising: an ultrasound source; said ultrasound sourceconfigured to subject a food product to ultrasonic waves; a first sourceof air heated to a temperature of approximately 190° F. to approximately210° F. and configured to circulate heated air around the food productfor approximately fifteen minutes; a second source of air heated to atemperature of approximately 170° F. to approximately 190° F. andconfigured to circulate heated air around the food product forapproximately fifteen minutes; and a third source of air heated to atemperature of approximately 150° F. to approximately 170° F. andconfigured to circulate heated air around the vegetables forapproximately one hour.
 60. An apparatus as recited in claim 59, whereinsaid first, second and third sources of heated air are configured tosaid head air through said housing at a rate of between approximately150 cubic feet per minute per square foot and approximately 450 cubicfeet per minute per square foot.
 61. An apparatus as recited in claim59: wherein said first source or air is configured to circulate heatedair at a rate of rate of between approximately 150 cubic feet per minuteper square foot and approximately 450 cubic feet per minute per squarefoot; and wherein said second source of air is configured to circulateheated air a rate of rate of between approximately 150 cubic feet perminute per square foot and approximately 450 cubic feet per minute persquare foot; and wherein said third source of air is configured tocirculate heated air at a rate of rate of between approximately 150cubic feet per minute per square foot and approximately 450 cubic feetper minute per square foot.